The present invention pertains to hearing aids. More particularly, the present invention pertains to suspension devices for hearing aid receivers.
The modem trend in the design and implementation of hearing devices is focusing to a large extent on reducing the physical size of the hearing device. Miniaturization of hearing device components is becoming increasingly feasible with rapid technological advances in the fields of power supplies, sound processing electronics and micro-mechanics. The demand for smaller and less conspicuous hearing devices continues to increase as a larger portion of our population ages and faces hearing loss. Those who face hearing loss also encounter the accompanying desire to avoid the stigma and self consciousness associated with this condition. As a result, smaller hearing devices, which are cosmetically less visible, but more sophisticated, are increasingly sought after.
Hearing device technology has progressed rapidly in recent years. First generation hearing devices were primarily of the Behind-The-Ear (BTE) type, where an externally mounted device was connected by an acoustic tube to a molded shell placed within the ear. With the advancement of component miniaturization, modern hearing devices rarely use this Behind-The-Ear technique, focusing primarily on one of several forms of an In-The-Canal hearing device. Three main types of In-The-Canal hearing devices are routinely offered by audiologists and physicians. In-The-Ear (ITE) devices rest primarily in the concha of the ear and have the disadvantages of being fairly conspicuous to a bystander and relatively bulky and uncomfortable to wear. Smaller In-The-Canal (ITC) devices fit partially in the concha and partially in the ear canal and are less visible, but still leave a substantial portion of the hearing device exposed. Recently, Completely-In-The-Canal (CIC) hearing devices have come into greater use. As the name implicates, these devices fit deep within the ear canal and are essentially hidden from view from the outside.
In addition to the obvious cosmetic advantages these types of in-the-canal devices provide, they also have several performance advantages that larger, externally mounted devices do not offer. Placing the hearing device deep within the ear canal and close to the tympanic membrane (ear drum) improves the frequency response of the device, reduces distortion due to jaw extrusion, reduces the occurrence of occlusion effects and improves overall sound fidelity. Earlier generation hearing devices function primarily by sound amplification and are typically not altered to a user""s particular hearing impairment. Modern electronics allow specific sound processing schemes to be incorporated into the hearing device. Similarly, custom programming can be incorporated into the hearing device circuitry allowing a truly custom device for any particular user.
While the performance of CIC hearing devices are generally superior to other larger and less sophisticated devices, several problems remain. Complications typically arise due to the small size of CIC hearing devices and the depth that they are inserted into a user""s ear canal. Additionally, the small size of the device, combined with increasingly complex electronics present other performance problems such as increased sensitivity to vibrations, more delicate components because of their small size, and the accompanying possibility of device failure.
The quality of the microphone system that receives sound waves is also critical to the performance of the hearing device. In general, hearing aids are configured with a microphone and a receiver (speaker) connected by an electronic circuit. The microphone picks up vibrational energy, i.e. sound waves, from the air or from the physical connection to the hearing aid. The physical connections can include the points where the hearing device shell and conducting wires join the receiver. A hearing device microphone transduces the sound waves into an electrical signal. The receiver (or speaker) then transduces the amplified electrical signal from the microphone and from any type of programming circuitry into vibrational energy which is then heard by a user. When driven by an electronic signal, the receiver itself will vibrate. Vibrations are also generated from within a user""s own skull. If the receiver is in contact with another hearing device component, these vibrations will be transferred from the receiver to the component, and from the component to the microphone. This often causes unwanted feedback. Typically this contact with other components occurs at the receiver port area, where the amplified sound exits the hearing device. This unwanted contact can also occur between a receiver wall and the hearing aid shell.
A known approach in larger hearing devices is to try and suspend the receiver away from the hearing device shell. However, in smaller hearing aids it is difficult to do this reliably. Receivers are typically suspended by means of two functional elements, the first being a piece of tubing connected to a port on the end of the receiver, and the second being an elastomeric sleeve about the body of the receiver can. The tubing and the sleeve can be configured as two components or integrated into a single piece suspension. In the single piece version, the tubing is molded as a unit with the sleeve about the receiver body. Non-woven fabric tapes are also commonly used to isolate the receiver from the shell wall.
Additionally, known receiver suspensions are typically made from a low durometer rubber such a silicone and neoprene. These devices are often molded with small bumps or flanges that help to reduce the contact area between the suspension and a shell wall. However, these molded suspensions present problems. First, since the hearing aid shell on custom hearing aids vary greatly from device to device, this often defeats the effectiveness of the small flanged features on the molded tips. This is due to contact between the shell and the receiver along larger surface areas or due to wedging the rubber suspensions too tightly along a shell wall.
Second, the elastomeric suspensions are generally glued into place in the hearing aid shell, or the receiver port. This glue can wick along the materials and harden the otherwise compliant materials, thus defeating the purpose of utilizing a receiver suspension. Also the molded suspensions are relatively large due to limitations in molding technology, the wire coming from the receiver can interfere with the suspension, and the wire attached to the receiver can contact the receiver and shell in uncontrolled ways thereby further contributing to feedback problems. Furthermore, lower durometer suspension tubes are delicate and susceptible to failure due to mechanical ingress caused by cleaning and probing, providing a direct ingress path for cerumen and other contaminates. Finally, silicone suspension tubes are very difficult to glue and attach because silicone compatible adhesives are generally slow to cure.
What is needed is a simple way of suspending the receiver away from the wall of the hearing aid shell without the addition of a large suspension apparatus. What is also needed is a receiver suspension that allows quick and simple installation and is essentially universal for a wide range of hearing devices.
A receiver suspension for isolating a hearing device receiver within a hearing device shell comprises a housing having an inside surface that defines a chamber, an open proximal end, and a distal end. The housing is adapted to be inserted into the hearing device shell. The receiver suspension also comprises a cover that is adapted to engage with the proximal end of the housing. An isolation membrane at least partially surrounds the hearing device receiver such that, upon insertion of the hearing device receiver into the housing, the isolation membrane suspends the receiver within the housing chamber. The isolation membrane prevents the receiver from contacting the inside surface of the housing. Preferably, the isolation membrane is formed from a stretched polymer material such as polyurethane or silicone and forms a series of pleats when engaged with the receiver.
In an alternate embodiment, a receiver suspension comprises a housing having an inside surface that defines a chamber, an open proximal end, and a distal end. The housing is adapted to be inserted into a hearing device shell. The receiver suspension also comprises a cover that is adapted to engage with the proximal end of the housing. An isolation spring is adapted to engage the hearing device receiver such that upon insertion of the hearing device receiver into the housing, the isolation spring suspends the receiver within the housing chamber. The isolation membrane prevents the receiver from contacting the inside surface of the housing. Preferably, the isolation spring comprises first and second grasping members and a flexure member intermediate to and connected with the first and second grasping members. The flexure member preferably includes a pair of spring biased portions that maintain the receiver at a specified distance from the inside surface of the receiver housing. The receiver suspension can alternately be formed from a multi-layered laminate material that provides frequency response dampening.